How is the prompt of "Measured value is inaccurate" on WCZ-2 proton magnetometer

1)   Estimated magnetic field and the actual magnetic field are quite different.
2)   Sensor is not well connected. Please check whether the sensor cable is short-circuited or broken.
3)   Sensor is open-circuited. Check the impedance of the sensor, nominal impedance should be about 12ohm.
4)   Noise is too high in that thunder or power line exists.